Various technologies for providing three-dimensional (3D) video content are currently investigated and developed. Especially, intense studies have been focused on various multiview applications wherein a viewer is able to see only one pair of stereo video from a specific viewpoint and another pair of stereo video from a different viewpoint. One of the most feasible approaches for such multiview applications has turned out to be such wherein only a limited number of input views, e.g. a mono or a stereo video plus some supplementary data, is provided to a decoder side and all required views are then rendered (i.e. synthesized) locally by the decoder to be displayed on a display. Several technologies for view rendering are available, and for example, depth image-based rendering (DIBR) has shown to be a competitive alternative. A typical implementation of DIBR takes a stereoscopic video and corresponding depth information with stereoscopic baseline as input and synthesizes an unlimited number of virtual views between the two input views.
However, in order to enable multiview rendering at the decoder side, texture data should be available at the decoder side along with the corresponding depth data. The depth information is usually a result of an estimation procedure based on stereo correspondences in input videos or an outcome of a noisy and low-resolution range sensor.
In both approaches of depth map estimation, the depth for each stereo camera view is estimated independently. As a result the independent processing, the resulting depth values estimated at different views can include inconsistencies among the views due to the presence of independent noise in each of the views.
A further source of inconsistency in multiview depth information may result from depth map compression, especially if carried out with conventional video compression systems, such as Advanced Video Coding standard H.264/AVC or the Multiview Video Coding MVC extension of H.264/AVC. These codecs are not optimized for depth data characteristics and may therefore introduce significant coding artifacts to the reconstructed depth data.
Thus, there is a need for improvements relating to depth map data consistency.